This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of the study is to investigate the effects of melatonin on the vestibulosympathetic reflex. The following hypotheses will be tested: melatonin will cause attenuation in MSNA of the vestibulosympathetic reflex;following the administration of melatonin, vascular responses to major arterial beds (i.e., forearm, calf, renal, coronary, etc.) will be attenuated during activation of the vestibulosympathetic reflex.;and melatonin will have a greater effect on the vestibulosympathetic reflex in women than men.